The present available silver brazing filler metals BAg25CuZn and BAg45CuZn contain silver contents respectively of 25% and 45% in their chemical compositions. Although BAg25CuZn and BAg45CuZn bear excellent silver brazing filler metal performance, their wettability and spreadability are much inferior to those of cadmium-containing silver brazing filler metals BAg35CuZnCd and BAg45CuZnCd, and also take on much higher solidus-liquidus temperatures. But due to cadmium adverse impact on operator's health and its pollution to the environment, particularly the implementation of EU ROHS Directive on Jul. 1, 2006, cadmium-containing material is being banned from usage gradually, thus employing BAg35CuZnCd and BAg45CuZnCd instead of BAg25CuZn and BAg45CuZn will certainly be limited. Therefore, research and development of cadmium-free silver brazing filler metal, which bears overall performance equavalent to or the same as those of BAg35CuZnCd and BAg45CuZnCd, with its silver content about 30% and solidus-liquidus temperatures lower than those of BAg25CuZn, not only bears good practicability and important economic value, but also benefit for environment protection.